Variometer with air dielectric



OCL 5, 1948. l J, M UNK 2,450,743

VARIOMETER WITH AIR DIELECTRIC Filed May 1, 1946 2 Sheets-Sheet 2 IN VUV TOR.

Patented Oct. 5, 1948 VARIOMETER WITH AIR DIELECTRIC Jacob Marinus Unk, Eindhoven, Netherlands, as-

signor, by mesne assignments, to Hartford National Bank and Trust Company, Hartford.

Conn., as trustee application May 1, 194s, serial No. 666,271 In the Netherlands July 15, 1941 Section 1, Public Law 690, August 8, 1946 Patent expires July 15, y1961 Claims.

The invention relates to a variable inductance of the variometer type the inductance variation of which is obtained by the relative rotation of two concentrically mounted coils which are arranged in such manner that the turns of the inner and of the outer coil are only separated by the airgap which is necessary for the required insulation between the inner and the outer coil whilst also the individual turns of each coil are separated from one another substantially by air as the dielectric.

It is already known to provide the turns of the inner and of the outer variometer coil on the outside and on the inside respectively of their supporting members in such -manner that the spacing between the inner and the outer coil may be reduced to the minimum which is dictated by considerations of mechanical nature and by the requirements of a satisfactory mutual insulation. It is thus possible to raise the coupling coefiicients of the two variometer coils to a maximum so that with similarly polarised variometer coils, the highest possible resulting inductance and, with oppositely polarised variometer coils, the smallest possible resulting inductance, l. e. the widest possible regulating range for the inductance is obtained.

In this case it was in general necessary, however, to ensure the rigidity of the coil construction by members which support the separate turns of the coil at a comparatively large number of points of the circumference whilst otherwise the required rigidity of the coil body can only be ensured by providing a hardening binding agent, for example a solution of Celluloid in an organic solvent. If it was desired to avoid the losses which are due to the presence of such insulating materials in the eld of the variometer, it was consequently necessary in any case to take into the bargain the complications and, if any, also the losses which are due to the presence of a fairly large number of supporting members in the field of the variometer.

The invention has for its object to provide a variometer of a construction free of losses and with a great variation of the inductance and to avoid the above-mentioned drawbacks.

To that end the support of the variometer coils which are on the outside coaxially cylindrical end which are formed by rectangular turns, consists of elongated insulating supporting members which extend transversely with respect to the planes of the turns of the said coils and which are secured exclusively to the faces of the coils, on the inside of the inner oil and on the outside of the outer coil respectively, whilst the supporting members of the inner coil are provided on either side with a shaft end the bearings of which are supported by the supporting members of the outer coil, and the latter members are connected by yokes arranged parallel to the shaft of the variometer on either side of the variometer coils, the rigidity of the spaced wireturns of the coils being in itself sufiicient to ensure the cylindrica1 shape of the variometer coils.

The above-described construction has the advantage that the faces of the variometer coils are kept assembled by the supporting members in a very rigid and exact manner Whilst it remains possible to reduce the spacing between the inner and the outer coil at this place to a minimum and to keep the variometer for the rest perfectly free from solid insulating material so that the freedom from losses of the whole unit is raised to the attainable maximum. It is possible in this case to secure the bearing of the two shafts in the inner coil in a particularly rigid manner to the supporting members of the outer coil so that here again a minimum number of components and, consequently, a minimum of losses may suffice,

It is advisible to secure the individual turns of the variometer coiltothe insulating supporting members by meansof open metallic clamping pieces which cannot form short-circuiting turns in the magnetic field of the variometer. It is thus possibleto secure the turns of the coil, for example by soldering, to the clamping pieces whilst the latter may be conformed in the most advantageous manner to the shape of the insulating supporting members.

It is also advantageous to utilize as supporting members of the variometer coil at each face an even number of cylindrical (ceramic) rods (preferably two), which are free from high-frequency losses and which engage-cylindrical holes of the metal connecting elements. In mechanical respect this solution is very simple owing to the cylindrical shape of the mutually matched supporting faces of the rod of the connecting element, Whilst use may be made of very simple methods of attachment such, for example, as soldering to a local metalization of the ceramic material.

With the above-mentioned construction with cylindrical ceramic supporting members the metal clamping pieces of the coils may advantageously be brought into clamping contact with the cylindrical supporting member through an angle of at least by pressing notches in the 3 metal one either side of the supporting member. It is thus possible to place the supports for the individual coil turns at the required mutual dis- -tances on the supporting members and then to secure them in the clamping pieces in a very simple manner by deformation of the metal beside the notches.

An increased security in mechanical respect can be obtained by the combination of the attachment by soldering and by clamping.

It is frequently advantageous to utilize as the current supply conductors for the inner movable variometer coil the two shaft ends on which slides on either side a metal contact spring which is secured to the ceramic supporting members of the fixed coil, preferably jointly with a connecting terminal, in a manner which corresponds to the manner of attachment of the individual coil turns, i. e. by means of metal clamping pieces secured to the supporting members. We thus obtain a very simple construction with which for supporting both the turns and the contact springs of the movable coil use may be made of similar standardized components conforming to the shape of the ceramic supporting members may be employed. Also the connecting terminals of the xed variometer coil may be secured in a similar mannerto the ceramic supporting members of the latter so that in a very favourable manner the four connecting terminals of the variometer may be provided two by two at the faces of the latter so as toAbe insulated without separate insulators being required therefor.

The invention will hereinafter be explained more fully with reference to the accompanying drawings which represent, by way of example, one embodiment thereof.

Fig. 1 shows a perspective view of a variometer according to the invention.

Figs. 2 to 8 represent partly in section constituent parts of this variometer in diierent mounting stages.

As the support for the xed variometer coil, which consists of halves I and 2, acts a construction which is formed by a top plate 3 and a bottom plate 4 of metal which are connected, by means of shrunk-on metal rings 6 to four cylindrical rods 5 of ceramic insulating material which is free from high-frequency losses as is commercially known, for example, under the registered trade-mark Calit. At regular distances clamping pieces 'I are clamped on and soldered to silverplated portions 26 of the rods 5, the separate turns of the fixed coil being provided on the said clamping pieces in such manner that each turn has at every face one point of support but for the rest is maintained in the exact shape owing to the natural rigidity of the metal wire employed.

In the clamping pieces are provided at I8 notches by means of which the rods 5 are clamped in the recesses of the clamping pieces 'I owing to the fact that material is pressed away therefrom and is forced over the rod 5 in such manner that the latter is fixed in the recess.

The connecting terminals 8 of the iixed coil are secured to the rods 5 in the same manner as the turns by means of clamping pieces I'I. A similar construction with insulating rods 9 and clamping pieces 'l is utilized for mounting the rotatable inner coil Ill, as is still partly visible in the inner aperture of the xed coil 2. By means of one of these rods 9 and of a clamping piece I6, the fixation of which likewise corresponds to that of the clamping pieces 1, each face of the rotatable coil Il has secured to it a shaft and II provided with a collar I2 on which slides a contact spring I3 which is secured in its turn to the rods I by means of a clamping piece I'I. At the left-hand shaft end the collar I3 carries, in addition, a member Il providedv with an vinsulating pin I5. a shrunk-on ring 6 and an insulating sector-shaped plate I9. The pin I5 consists of the same insulating rod-material as the rods 5 and 9 whilst the shrunk-on rings 6 are completely similar to the shrunk-on rings provided on the rods 5.

Figs. 2a and b represent in section a clamping piece I'I which has a threaded hole 20 for the attachment of the connecting terminals l and, as the case may be, the contact springs I2 to the rods 5.

Figs. 3a and b show how from the same moulding a clamping piece I6 having a bearing 2| may be produced by boring away the central portion.

Figs. 4 and 5 represent insulating rods 5 and 9 which are designed to support the rotatable and the xed variometer coil respectively and which are provided with layers '22 of silver at those points to which the clamping pieces for the various components of the coil are to be soldered, as may be seen from the Figs. 6 and 7. These layers of silver are preferably formed by bumng-in on the ceramic material of the rod and, in addition, as the case may be by electrolytically precipitating a film of silver on the burnt in silver layer.

Fig. 6 shows the assembling of two rods 9 with a clamping piece 2| for the shaft of the variometer and with clamping piece 'I for the windings. At 23 the insulating rods 5 and 9 are freed, for example by grinding, from silver in order to avoid short-circuiting turns in the eld of the coil. In Fig. 7 a contact spring I3 is shown at its definitive place whilst it is distinctly visible that it may make contact on the rotor shaft according to Fig. l through the intermediary of the collar I2. The pronounced analogy in the .assembling of the supporting members for the rotatable and the fixed coils of the variometer appears very distinctly from Figures 4 to 7.

The same remarks apply to Fig. 8 which shows in section how rods 5 and l to which variometer coils I and I0 are secured by means of clamping pieces I (not shown) are united, jointly with two clamping pieces I5, a shaft end I I, a collar l2 and a screw 24 so as to form a mechanical unit. For both coils similar supports are utilized, they are only arranged in mutually opposite positions. It may also be seen in this figure how the contact spring I3 slides on the collar I 2 and thus may act as a current supply conductor for the rotatable variometer coil Ill of which the end concerned is soldered to the corresponding clamping piece I6. In the manufacture of induction coils according to the invention use may be made with advantage of a method according to which the insulating rods each of which is previously united with the required number of connecting members to form a single unit are assembled in the correct position in a iig jointly with the coil winding that has previously been shaped into the correct form, after the required soldering material and ilux are inserted between the metal parts to be connected, the aggregate of jig and coil being then immersed in a temperature bath, preferably an oil bath, whose temperature exceeds the melting point of the soldering material.

This method has the advantage that the accuracy of reproduction of the coil dimensions is remarkably satisfactory, that any diilculty that may occur in the normal soldering method if the turns were to be laid in position on the rods are obviated and that any excess soldering material existing outside the surfaces to be connected is deposited in the temperature bath and is prevented by the presence of the latter from depositing between the turns to the detriment of the insulation of the coil.

It is also advantageous that subsequent to the above described operation the coil should be provided with a thin metal layer, for example of silver or gold, by any of the usual methods so that both the coil turns and the other metal constructional parts of the coil are coated with a continous metal layer. Apart from the well-known improvement upon the high frequency conductivity of the coil this ailords a particularly satisfactory appearance and a satisfactory protection of the metal parts against atmospheric influences. This method is particularly advantageous for the manufacture of variometers according to the present patent application since thus that the attachment of the variometer turns to insulating rods through the intermediary of metal clamping pieces that may be realized completely. Also the alternate attachment of the turns to the rods may be employed, with which every other turn of the winding is secured to a determined insulating rod. If in this case the width of the clamping pieces 'l is assumed to be equal to th`e thickness of the winding wire and to the spacing between the successive turns, we obtain a surface leakage path 21 which amounts to three times the spacing of the turns, the security of the coil against sparkover between the turns being thus highly increased.

The variometers produced can readily be manufactured in standardized series of regularly increasing dimensions with the aid of the same tools whereas with the known variometer constructions it is generally necessary to keep in store for every new series a new set of components, for example comparatively complicated insulating pieces.

Owing to its rigid construction the variometer according to the invention may be manufactured with great precision and with a comparatively small airgap between the rotatable and ilxed coils and, consequently, with a large coupling coeilicient. With an airgap of 1.5 mms. it is possible, 011' xample, to obtain an inductance variation of What I claim is:

l. A variable inductance of the variometer type comprising an inner and an outer coil, the convolutions ot each coil being formed substantially to outline a rectangle with equal lengths between the end portions and with widths between the side portions of progressively varying dimensions in progressively adjacent convolutions, so the side portions of the convolutions lie on the outlining planar locus of a cylinder, the dimensions of the inner coil being suiilciently smaller than the dimensions of the larger coil to permit free rotary movement of the inner coilrelative to the outer from each other solely by air as a dielectric and the rigidity of the respective convolutions being suillcient to maintain the cylindrical shape of the two coils, means for supporting the outer coil and consisting of elongated ceramic members disposed substantially perpendicular to the planes of the convolutions, means securing the end portions of each convolution on its outer edges to said ceramic members, elongated vceramic supporting members for the inner coil similarly disposed substantially perpendicular to the planes of the convolutions, and means securing the end portions of each convolution on its inner edges to the ceramic supporting members, means for supporting the ceramic supports for the outer coil, means on those outer coil ceramic supports constituting a bearing at each end of the outer coil, and shaft ends secured to the ceramic supports of the inner coil and iitting in the bearings supported on the outer ceramic supports, and serving to support the inner coil for rotation in those bearings.

2. A variometer as claimed in claim 1, including open metal clamping pieces that secure the individual convolutions of the coils to the ceramic supporting members.

3. A variometer as claimed in claim 1, including open metal clamping pieces that secure the individual convolutions of the coils to the ceramic supporting members, in which the ceramic supporting members at each end or face of the coils consist of an even number of cylindrical rods, having spaced metallized areas, and the metal clamping pieces are secured to the rods at the metallized areas by soldering.

4. A variometer as in claim l, including open metal clamping pieces that secure the individual convolutions of the', coils to the ceramic support` ing members, in which the ceramic supporting members at each end or face of the coils consist of an even number of cylindrical rods, having spaced metallized areas, and the metal clamping pieces are secured to the rods at the metallized areas by soldering, the metal-clamping pieces engaging the -supporting rods with a contact through an angle of at least 5. A variometer as in claim 1, including means for supplying current to the movable inner coil, said means including metal contact springs insulatingly supported on the ceramic supporting members for the xed outer coil to engage the corresponding shaft ends for the inner coil.

JACOB MARINUS UNK.

REFERENCES CITED The following references are oi' record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,550,243 Copp Aug. 18, 1925 1,559,186 Heitzman Oct. 27, 1925 FOREIGN PATENTS Number Country Date 249,315 Great Britain Mar. 25, 1926 

